Magnetic bearings are often used in high speed rotating machinery to support a shaft or rotor using electromagnetic force to levitate or support the rotor without physical contact. A typical magnetic bearing assembly includes a shaft, a rotor that rotates with the shaft, a stator that remains stationary, and control coils for controlling the axial and radial displacement of the rotor. Position sensors are used to sense the axial and radial displacement of the rotor. A controller uses the output from the position sensors to vary the current in the control coils to adjust the axial and radial displacement of the rotor and the shaft to which the rotor is attached.
Prior magnetic bearing assemblies have located the position sensors adjacent to the control coils, which can result in electromagnetic and thermal interference between the control coils and the measurement coils used in the position sensors. Other approaches include locating a part of the position measuring apparatus in the shaft, which increases the size of the magnetic bearing assembly. Prior designs can also require separate position sensors for sensing axial and radial shaft position. Using separate sensors to sense axial and radial position increases the size and complexity of the magnetic bearing assembly.
Accordingly, in light of these difficulties, there exists a need for a magnetic bearing assembly with position sensors that are located separately from the control coils and that are efficiently positioned to reduce the size of the magnetic bearing assembly.